1. Field of the Invention
The present invention relates to automated currency processing and, more specifically, to the automated detection of transparent window security features and defects present in polymer bank notes undergoing high-speed processing.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In an effort to combat the counterfeiting of bank notes and other machine-processable security documents, substrate manufactures continue to develop and incorporate new security features into their product. A leap in security technology occurred when polymer substrates were introduced. Polymer bank notes (and some new cotton bank notes) allow security features never before available with traditional cotton-fiber bank notes. One such security feature is the incorporation of a transparent window that penetrates the bank note substrate, sometimes extending to one edge of the note.
Current bank note processing machines feature numerous detectors and sensors to determine various attributes of a bank note being processed. One such detector monitors each note for excessive damage, such as perforations or tears. If the detector senses areas of a note through which light may pass, the note is rejected or even automatically shredded if the processor features note destruction capabilities. This type of action is perfectly suitable for cotton-fiber bank notes which were never intended to have perforations. However, such detection method fails when a bank note having the new window security feature is encountered.
If bank notes having the new transparent window feature were processed by a current high-speed processing machine having perforation defect detection, the machine would sense the intentional transparent window as a hole or perforation and reject the note as damaged. Accordingly, a need exists for a new type of bank note defect detector that can differentiate the transparent window security feature in a polymer or some other substitute note from a perforation. If the transparency is on the edge of the note then the note size calculations are wrong and the machine ability to process the note is compromised as the machine cannot find the leading or the trailing edge of the note being processed causing an erroneous “jam” or stoppage condition.